The week in pictures: 21 September 2012

Phobos, one of Mars' two small moons, partially obscures the sun in this image captured by Nasa's Curiosity rover. Curiosity outfitted its high-resolution camera with protective filters and took pictures of the sun as Phobos sailed by. It was a tricky shoot. Phobos and its sister moon Deimos are closer to Mars than our moon is to Earth, so they shoot across the sky relatively quickly. Phobos takes less than eight hours to circle Mars.Picture: REUTERS/NASA/JPL-Caltech/MSSS